The purpose of this study is to determine the relative efficacy of conventional therapy (continuous daily OCP) compared to that of leuprolide in preventing endometrial shedding and vaginal bleeding in female patients undergoing bone marrow transplants. To determine the relative toxicity of these regimens with respect to known side effects. To compare the frequency of subsequent chronic morbidity such as gonadal failure, failure of sexual maturation & sexual dysfunction. To determine if inhibin levels are a predictor of gonadal failure.